The purpose of this proposal is to understand the relationship between membrane arcitecture and function in photosynthetic membranes. Our approach will be via discrete, yet correlative, techniques using the unicellular blue-green alga, Synechococcus cedrorum. Our strategy will consist of four major experimental techniques: (1) the isolation of temperature-sensitive mutants that are defective in photosynthesis; (2) characterization of the mutants as to the photosynthetic aberration and structural defect. This will be done using fluorescence, photosystem activities, gel electrophoresis, and electron microscopy; (3) isolation of membrane fragments that are highly enriched in Photosystem 1 and 2 function; (4) use of transformation for genetic mapping studies. The specific goals of the proposal should yield the following types of information: (1) the protein composition of photosynthetic photosystems 1 and 2; (2) the functional characteristics of such isolated photosystems; (3) the effect of specific mutations on the structure and function of the membranes; (4) a more precise undestanding of the mechanism of fluorescence in photosynthesis; (5) the lcoalization of the photosystems as to whether they are on the internal or external part of the membrane; (6) a straightforward and reproducible means of genetic transfer in blue-green algae; and (7) mapping of the algal genome and some idea of the number of different genes involved in the structure and development of the photosynthetic lamellae.